For the average cycling fan, road racing brings more glory. Yes, being World Champion is more prestigious, but which is the percentile of cycling fans who care about off road cycling?
If MVDP cares for mainstream prestige, road is way more important for that. And I watch a lot of cross and MTB. But we can't deny the facts and those are that if some rider wants a crack at mainstream glory, he needs to go to the road.
Of course he can stay in MTB or Cross and be known as a glory in a small niche, but apart from the few who follow it, few persons know about Absalon, Schurter, Peat, Minnaar, Anne-Caroline Chausson, etc.
I too want for MTB and CX to be more recognized. But they are still a good years away from that.